1. Technical Field
The invention relates to an electro-dynamic exciter e.g. for use in activating a resonant panel-form radiator loudspeaker of the kind described in co-pending parent application Ser. No. 08/707,102.
2. Background Art
More particularly, the present invention is an electro-dynamic inertial vibration exciter, e.g. of the general kind described in parent application Ser. No. 09/011,773 which describes an inertial vibration exciter comprising a motor coil assembly having a c oil rigidly fixed to a tubular coil former, a magnet assembly disposed concentrically with respect to the motor coil assembly and forming an inertial mass, and resilient means supporting the magnet assembly for axial movement relative to the motor coil assembly, and wherein the tubular member, is adapted to be rigidly mounted directly to a member to be vibrated, e.g. a resonant panel loudspeaker, by adhesive means.
The present invention relates to the efficient construction of exciters and to manufacturing techniques for producing such exciters.
According to the invention an electro-dynamic inertial vibration exciter for exciting a member having capability to sustain and propagate input vibrational energy and comprising a motor coil assembly having a coil rigidly fixed to a coil former member, a magnet assembly disposed concentrically with respect to the motor coil assembly, and movable axially relative to the motor coil assembly, on an axially compliant suspension is characterised by a carrier supporting the motor coil assembly and adapted for connection to the member to be excited. The carrier may be directly connected to the coil former member. The suspension means may be connected to the carrier. A coupling member may be connected to the carrier via the suspension member, which coupling member is adapted to carry the magnet assembly.
The coupling member and the magnet assembly may be adapted to interfit one with the other, and means may be provided on the coupling member and on the magnet assembly for fixing the coupling member and magnet assembly together. The fixing means may comprise at least one chip. The carrier and the suspension member may be integral. The coupling member and the suspension member may be integral. The suspension may be resilient. The suspension may be formed as a diaphragm. Alternatively the suspension may comprise a set of resilient arms. The coupling member and the carrier may be annular and the arms may be connected between the coupling member and the carrier to extend circumferentially.
The carrier may have a face adapted for contact with the resonant member and arranged to be fixed thereon, e.g. by adhesive means or by fastening devices. The carrier may be formed integrally with a flange arranged to be fixed to the resonant member. The flange may be disc-like and arranged to support the exciter in a cavity in the resonant member by an edge portion of the flange. The disc may be arranged to close the cavity.
An end of the coil former member may be located and mounted in a recess in the carrier. The coil may be mounted on the outer face of the coil former member.
The magnet assembly may comprise opposed generally disc-like pole pieces sandwiching a magnet, the periphery of one of which pole pieces being disposed within and adjacent to the motor coil assembly, and the periphery of the other of which pole pieces being formed with an upstanding flange arranged to lie adjacent to and to surround the motor coil assembly. The flange may be adapted to interfit with the coupling member. A lip may be formed on the flange, which lip is shaped to interfit with the coupling member, and fixing means on the coupling member may be adapted to engage the lip. A dust seal may be arranged to close the annular coil carrier.
The axially compliant suspension for the magnet assembly may comprise a pair of axially spaced suspension parts or components to facilitate the axial guidance of the voice coil with respect to the motor coil assembly. The suspension parts may be of any desired form, e.g. they may comprise respective sets of resilient arms. The respective outer ends of the resilient arms in each suspension part may be coupled together by posts, the lower ends of which form feet adapted for contact with the resonant member. The inner ends of the arms may carry respective annular coupling members adapted to carry the magnet assembly.
From another aspect the invention is a loudspeaker comprising an inertial vibration exciter as described above.